B737 First Officer reports departing with low engine oil quantity after maintenance was unable or unwilling to service the aircraft prior to departure. Oil quantity in-flight decreased further and the crew elected to return.

Narrative

We made a precautionary return to departure airport due to low oil quantity. Upon preflight inspection of the aircraft; we noticed the quantity was 8 quarts in the left engine and 9 quarts in the right. Captain called maintenance to see if we could get some oil added and they advised the quantity was sufficient to make it to destination. Shortly after takeoff; we noticed 2 quarts displayed in the left and 1 quart in the right. We leveled off according to procedure; reduced the power and advised the tower of a possible return. The left engine was now displaying 1 quart (matching the right) and after 30 seconds; we decided to return to the field. Our landing weight was under gross and we had normal indications for oil temperature and pressure. Upon return to the gate; the Captain called company and maintenance arrived; adding 9 quarts of oil to the left engine and 8 quarts to the right. The aircraft landed the previous evening with 6 quarts of oil in the left engine and 7 in the right. Had oil been added; this event would not have occurred.